The present invention relates to the composition and use of water-soluble or water-dispersible copolymers for oil field applications. Specifically, the present invention relates to polymers containing allyloxy linkage and its functional derivatives for use in oil field applications as fluid additives for drilling and cementing processes.
Polymers are used extensively in oil field application as fluid additives for drilling, cementing, gas and oil well fracturing and enhancedxe2x80x94oil-recovery processes. Synthetic, organic, and inorganic polymers, as well as cellulose ethers and guar gum and guar derivatives, are widely used in oil field applications. These materials are also applied in a variety of formation-damage control applications and as dispersing agents.
In the initial drilling operation of an oil or gas well, a drilling fluid, commonly referred as xe2x80x9cdrilling mud,xe2x80x9d is pumped under pressure down to a string of drill pipes through the center of the drilling bit, back through the space or annulus between the outside of the drilling stem and the borehole wall, and finally back to the surface. After a well has been drilled and oil discovered, one or more subterranean, hydrocarborn-producing formations are most often encountered. The well is then completed to obtain the maximum hydrocarbon production from the subterranean producing formations.
Completion of a well refers to the operations performed during the period from drilling-in the pay zone until the time the well is put into production. These operations may include additional drilling-in, placement of downhole hardware, perforation, sand control operations, such as gravel packing, and cleaning out downhole debris. A completion fluid is often defined as a wellbore fluid used to facilitate such operations. The completion fluid""s primay function is to control the pressure of the formation fluid by virtue of its specific gravity. The type of operation performed, the bottom hole conditions, and the nature of the formation will dictate other properties, such as viscosity. Use of completion fluids also clean out the drilled borehole. Oil well cement compositions are used in the completion operation to make a permanent, leak proof well for continuous use.
In cementing operations of gas or oil wells, a hydraulic cement is normally mixed with sufficient water to form a pumpable slurry and the slurry is injected into a subterranean zone to be cemented. After placement in the zone, the cement slurry sets into a hard mass. In primary cementing , where a cement slurry is placed in the annulus between a casing or liner and the adjacent earth formations, loss of fluid is a major concern. The formations can result in premature gelation of the cement slurry and bridging of the annulus before proper placement of the slurry. In remedial cementing operations, the control of fluid loss is necessary to achieve the more precise cement slurry placement associated with such operations.
Among all other slurry properties, fluid loss control is one of the critical concerns for cement slurry formulation, especially at high temperature, high pressure (squeeze cement) and salt environments. The main purpose of fluid loss additives is to prevent the dehydration of the cement slurry that can reduce its pumpability as well as affecting its other designed properties. Loss of a significant amount of water from the cement slurry can cause changes in several important job parameters, such as reduced pumping time and increased frictional pressure. Fluid loss additives are used to help prevent water loss from cement slurries to the rock formation as the slurry is pumped into the annulus between the casing and the well bore. This allows displacing the maximum amount of mud, compressive strength development, and bonding between the formation and the casing. In fact, under harsh conditions and due to permeable zones, the slurry can dehydrate quickly and become unpumpable, preventing the extension of slurry into voids and channels, particularly where the annular space between the liner and the open hole is too narrow. Any bridging problem due to high fluid loss would considerably disturb the cement job and affect the integrity of the cement column.
Deep oil wells are generally subjected to high temperature gradients that may range from 40xc2x0 F. at the surface to 400xc2x0 F. at the bottom hole. The geology of the well traversed may also contain environments, such as massive salt formations, that can adversely affect the cementing operation.
In general, two types of fluid loss additives are used in the cementing industry. They are classified as low temperature ( less than 230xc2x0 F.) or high temperature ( greater than 230xc2x0 F.) fluid loss additives (xe2x80x9cFLACsxe2x80x9d). Synthetic polymers and derivatives of polysaccharides are used in oil field operations from the drilling fluids to the completion fluids as well as in oil well cements.
Partially hydrolyzed polyacrylamide and copolymers of acrylamide, and sodium acrylate, acrylic acid are commonly used in the oil field. Replacing the acrylamide amide hydrogen atoms by other groups reduces the hydrolysis rate and increases viscosity in brines of the polymers. Homopolymers and acrylamide copolymers of 2-acrylamide-2-methylpropanesulfonic acid and salts, N-methylacrylamide, N-isopropylacrylamide , N-butylacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylacrylamide and other N-alkylacrylamides have been disclosed for use in polymer flooding. Terpolymers of acrylamide, acrylic acid and 2-hydroxypropylacrylate prevent fluid-loss in drilling mud. Other monomers such as N-vinylpyrrolidinone, vinylchlroide, vinylsulfonate, styrene and styrene sulfonate, maleic anhydride and various vinyl acrylates are also used in copolymerizing acrylamide or acrylic acid for drilling fluid applications. However, these conventional acrylamide copolymers are not hydrolytically and thermally stable at severe operating conditions such as under extreme high temperature and high salt content and a caustic environment.
Examples of polysaccharides derivatives are cellulose ether compounds such as methylcellulose(MC), ethylcellulose(EC), carboxymethylcellulose(CMC), hydroxyethylcellulose(HEC), hydroxypropylcellulose(HPC), carboxymethylhydroxyethylcellulose(CMHEC), ethylhydroxyethylcellulose (EHEC) and hydrophobically modified hydroxyethylcellulose(HMHEC). Examples of guar derivatives are hydroxyethyl guar and hydroxypropyl guar. These cellulose and guar compounds are used in drilling fluids and cementing spacers to suspend solid particles, and in fracturing fluids to suspend sand and other proppants and to prevent fluid loss in these applications. However, due to its polysaccharide structure and acetal linkage, these naturally derived materials are subject to hydrolysis at temperature above 350xc2x0 F. and high levels of salt in deep well conditions.
U.S. Pat. Nos. 4,895,663, 4,895,664 and 4,944,885 (Chen) disclose using copolymers of acrylic acid and sodium 3-allyloxy 2-hydroxypropanesulfonate (AHPS) as a scale inhibitor and deposti control agent for cooling water treatment.
Water soluble copolymers containing 2-acrylamido-2-methylpropanesulfonic acid (AMPSR) are described in U.S. Pat. Nos. 3,898,037; 4,641,793 and 4,717,542. The copolymers are used for water treatment in general.
U.S. Pat. No. 5,032,995 (Matz et al.) discloses an amphoteric copolymers containing nonionic, anionic and cationic monomers for use as deflocculants in drilling mud.
U.S. Pat. No. 5,169,537 (Chen) discloses using terpolymers of acrylic acid, 3-alloxy-2-hydroxypropanesulfonate and sodium 3-allyloxy 2-hydroxypropanesulfonate as a scale inhibitor.
U.S. Pat. No. 5,403,821 (Shioji) describes water soluble anionic copolymers containing carboxylic acid and allyl ether sulfonate moieties, having an average molecular weight of 1,000 to 50,000 as drilling additives for stabilizing muddy water.
None of the aforementioned prior art describes the specific copolymers of the present invention for oil field applications, especially in cementing as fluid loss additives (FLAC). Hence, a need still exists in the oil field industry for thermally and hydrolytically stable materials for use in high temperature oil field applications.
The present invention relates to copolymers containing allyloxy linkage and its functional derivatives as oil field fluid loss additives in drilling operations. Specifically, copolymers containing acrylamide, and 3-allyloxypropanesulfonate (xe2x80x9cAHPSxe2x80x9d) and other monomers are synthesized for the applications. The AHPS component of the copolymers is thermally and hydrolytically stable at high pH, saturated salt and elevated temperature conditions. Copolymers of the invention are efficacious as oil well cement slurry additives for rheology and fluid loss purposes, especially at high temperatures.
The present invention also relates to an oil filed cement composition comprising cement and the above mentioned copolymers as a fluid loss additive.
The present invention also comprehends an oil field fluid composition comprising the above mentioned composition and at least one oil field ingredient.
Surprisingly, it has been discovered that certain water-soluble or water dispersible copolymers are effective in preventing fluid loss in oil field cementing applications and in oil field fluids from drilling fluids to completion fluids.
The present invention relates to copolymers containing allyloxy linkage and its functional derivatives for oil fluid loss application. Specifically, copolymers containing acrylamide and 3-allyloxyhydroxypropanesulfonate (AHPS) and other monomers are synthesized. The AHPS component of the copolymers is thermally and hydrolyticly stable at high pH, in saturated salt, and at elevated temperature conditions. Copolymers of the invention are especially efficacious as oil well cement slurry additives for rheology and fluid loss purposes, especially at high temperature.
One component of the copolymer of the present invention comprises monomeric repeat unit(s) of alpha, beta ethylenically unsaturated compound of Formula (I)
"Parenopenst"E"Parenclosest"xe2x80x83xe2x80x83Formula (I)
Wherein E is the repeat unit obtained after polymerization of an alpha, beta ethylenically unsaturated compound, preferably a carboxylic acid, an amide form of the carboxylic acid, and a lower alkyl (C1-C6) ester or hydroxylated lower alkyl (C1-C6) ester of such carboxylic acid. Compounds from which E may be derived include the acrylic acid, methacrylic acid, acrylamide, maleic acid or anhydride, itaconic acid, crontonic acid, fumaric acid, styrene, styrene sulfonate, vinyl pyrrolidone, N-methylacrylamide, N-isopropylacrylamide ,N-butylacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylacrylamide and other N-alkylacrylamides. Water-soluble salt forms of the carboxylic acids are also within the purview of the invention.
Another component of the copolymers is the repeat unit formed by the polymerization of a monomer containing sulfonate functionality as shown in Formula (II) 
wherein R1 is hydrogen or a lower alkyl (C1 to C5), R2 and R3 are identical or different and denote hydrogen, or C1 to C5 alkyl groups; and, M is hydrogen or a water-soluble cation (e.g., NH4+, alkali metal). 2-Acrylamido-2-methylpropanesulfonic acid (AMPSR) is a typical example of a Formula (II) monomer. However, compounds such as styrene sulfonate, vinyl sulfonate and allyl sulfonate also fall in the category.
A third component of the copolymer is the repeat unit formed by the polymerization of a substituted allyl alkylene ether compound as shown in Formula (III), 
Wherein R1 is hydrogen or lower alkyl (C1-C5), R4 is a hydroxyl substituted alkylene group having from 1 to about 6 carbon atoms or a non-substituted alkyl or alkylene group having from 1 to about 6 carbon atoms; X is an anionic radical (e.g., sulfonate, phosphate, phosphite or phosphonate); and, Z is one or more hydrogen or a water soluble cation or cations which together counterbalance the charge of X. Compounds encompassed by Formula (III) include the repeat unit obtained after polymerization of 3-allyloxyhydroxypropanesulfonate, 3-allyloxyhydroxypropanesphosphite, and 3-allyloxyhydroxypropanesphosphate.
It is noted that more than one monomer unit in Formula I, II and III mentioned above may be present in the copolymers of the invention. Therefore, the polymer of the present invention is comprised of copolymer, terpolymer and tetrapolymer or more wherein two, three, four or more different monomeric repeat units selected from the repeat units described in Formulas I, II, and III are present in the polymer. There is no limit to the kind and mole percent of the monomers chosen so long as the total mole percent adds up to 100 mole % and the resulting copolymers are water soluble or water dispersible.
Branching or cross-linking agents such as methylenebis(meth)acrylamide, polyethyleneglycol di(meth)acrylate, hydroxyacrylamide, allyl glycidyl ether, glycidyl acrylate and the like may also be added for the copolymers.
Solution, emulsion, and dispersion or gel polymerization techniques may be used to polymerize the monomers described. Conventional polymerization initiators such as persulfates, peroxides and azo type initiators may be used. Polymerization may also be initiated by radiation or ultraviolet mechanism. Chain transfer agents such as alcohols (preferably isopropanol), allyl alcohol, amines or mercapto compounds may be used to regulate the molecular weight of the polymer. It is to be understood that the aforementioned methods of polymerization do not in any way limit the synthesis of polymers according to this invention.
A preferred copolymer composition comprises (A) acrylamide or a substituted acrylamide; (B) a monomer containing sulfonate functionality; (C) of a substituted allyl alkylene ether compound; and, (D) of a monomer containing carboxylic acid functionality wherein the mole percentages of components (A), (B), (C) and (D) are from 5% to 95% with the proviso that the sum of mole % is 100.
The components are preferably present in the following mole percentages, wherein (A) is preferably from about 20 mol % to about 70 mol %, (B) is preferably from about 20 mol % to about 60 mol %, (C) is preferably from about 5 mol % to about 40 mol % and (D) is preferably from about 5 mol % to about 40 mol % with the proviso that the sum of the mol % is 100%. (A) is most preferably from about 40 mol % to about 60 mol %, (B) is most preferably from about 30 mol % to about 50 mol %, (C) is most preferably from about 10 mol % to about 30 mol % and (D) is most preferably from about 10 mol % to about 30 mol % with the proviso that the sum of the mol % is 100%.
Several aspects of the invention include copolymers of acrylamide /sodium 2-acrylamido-2-methylpropanesulfonate/3-alloxy-hydroxypropanesulfonate (AHPS) of Formula (IV) 
and acrylamide /sodium 2-acrylamido-2-methylpropane sulfonate/sodium 3-allyloxy-2-hydroxypropanesulfonate/N-vinylpyrrolidone of Formula (V), 
and acrylamide /sodium 2-acrylamido-2-methylpropanesulfonate/ sodium 3-alloxy-hydroxypropanesulfonate (AHPS)/acrylic acid of Formula (VI), 
wherein R1 is independently selected from hydrogen or lower alkyl (C1-C5), M is H or water soluble cation. The mole percent (m, n, o, p) for each of the monomers in the copolymers (IV), (V) and (VI) is in a random distribution to the extent of 5% to 95%. However, the sum of the components is 100 mole percent and the resulting copolymer is still water soluble or water dispersible.
The compound, 2-acrylamido-2-methylpropanesulfonic acid (AMPSR) is commercially available from the Lubrizol Corporation. Sodium 3-allyloxy-2-hydroxypropanesulfonate (AHPS) is available from BetzDearborn Division of Hercules Incorporated.
The copolymer compositions may also be used in combination with polysaccharides including cellulose ether compounds such as those selected from hydroxyethylcellulose, cationic hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, hydroxypropylcellulose, carboxymethylcellulose and blends thereof; starch and starch derivatives such as those selected from straight starch, pregelenatised starch, cationic starch, styrene butadiene starch, carboxymethylstarch, hydroxypropylstarch, hydroxyethylstarch and blends thereof; and guar and guar derivatives selected from straight guar, carboxymethylguar, hydroxypropylguar, carboxymethylhydroxypropylguar, cationic guar and blends thereof.
The polymers should be added to the system, in an amount effective for the specific application. This amount will vary depending upon the particular system for which treatment is desired and will be influenced by factors such as, type and composition of cement, pH, temperature, water quantity and the respective concentrations.